Touch sensitive element having beads dispersed in an electroactive layer and display device including the same

ABSTRACT

The touch sensitive element according to an exemplary embodiment of the present disclosure includes an electroactive layer, an electrode, and a plurality of beads. The electroactive layer includes an electroactive polymer. The electrode is disposed on at least one surface of the electroactive layer. The plurality of beads is dispersed in the electroactive layer and has a diameter larger than the thickness of the electroactive layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Republic of Korea PatentApplication No. 10-2016-0160107 filed on Nov. 29, 2016, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND Field

The present disclosure relates to a touch sensitive element and adisplay device including the same, and more particularly, to a touchsensitive element with an improved vibration strength and a displaydevice including the same.

Description of the Related Art

A touch element is a device which senses a user's touch input such asscreen touch to a display device or a gesture and is widely utilized fordisplay devices of a public facilities and a large size display devicesuch as a smart TV, in addition to a portable display device such as asmart phone or a tablet PC. An operation type of the touch element mayinclude a resistive type, a capacitive type, an optical type, andelectromagnetic (EM) type.

However, recently, in addition to sensing of the user's touch input,studies on a haptic device which transmits a tactile feedback sensed bya finger of the user or a stylus pen of the user as a feedback for theuser's touch input are being performed.

Such a haptic device, a haptic device to which an eccentric rotatingmass (ERM) is applied, a haptic device to which a linear resonantactuator (LRA) is applied, and a haptic device to which a piezo ceramicactuator is applied are used. However, the above-mentioned hapticdevices are configured by an opaque material and do not vibrate aspecific part of the display device, but rather vibrate the entiredisplay device. Further, the above-mentioned haptic devices do notprovide various vibration feelings and easily break due to an externalimpact because of low durability of the haptic devices.

In order to solve the above-described problems, a haptic device whichuses an electroactive polymer (EAP) is studied. Since the haptic devicewhich uses the electroactive polymer is thin and flexible, the hapticdevice may be easily applied to various display devices. However, thehaptic device which uses the electroactive polymer has problems in thata vibration strength is lower than the ERM, the LRA, and the piezoceramic actuator and a driving voltage is high.

SUMMARY

An object to be achieved by the present disclosure is to provide a touchsensitive element which has an excellent vibration strength by improvinga blocking force of a touch sensitive element and a display deviceincluding the same.

Further, another object to be achieved by the present disclosure is toprovide a touch sensitive element which may transmit tactile feedbackwith an excellent vibration strength even though the touch sensitiveelement is disposed below the display panel and a display deviceincluding the same.

Objects of the present disclosure are not limited to the above-mentionedobjects, and other objects, which are not mentioned above, can beclearly understood by those skilled in the art from the followingdescriptions.

According to an aspect of the present disclosure, there is provided atouch sensitive element including an electroactive layer including anelectroactive polymer; a first electrode electrically coupled to asurface of the electroactive layer; a second electrode electricallycoupled to a same surface or a different surface of the electroactivelayer as the first electrode, the electroactive layer configured tovibrate responsive to applying a voltage difference between the secondelectrode and the first electrode; a plurality of beads dispersed in theelectroactive layer, the plurality of beads having a diameter that islarger than a thickness of the electroactive layer. Therefore, at leastone surface of the electroactive layer is formed to be convex along thesurfaces of the plurality of beads and the surface area of theelectroactive layer is increased. Accordingly, the blocking force of thetouch sensitive element may be improved and the vibration strength ofthe touch sensitive element may be improved.

According to another aspect of the present disclosure, there is provideda touch sensitive element comprising: an electroactive layer includingan electroactive polymer; a first electrode electrically coupled to asurface of the electroactive layer; a second electrode electricallycoupled to a same surface or a different surface of the electroactivelayer as the first electrode, the electroactive layer configured tovibrate responsive to applying a voltage difference between the secondelectrode and the first electrode; and a plurality of beads dispersed inthe electroactive layer, the plurality of beads having a Young's modulusthat is greater than a Young's modulus of the electroactive polymer.

According to another aspect of the present disclosure, there is provideda display device including a display panel which displays an image and atouch sensitive element below the display panel. The touch sensitiveelement includes: an electroactive layer; a first electrode electricallycoupled to a surface of the electroactive layer; a second electrodeelectrically coupled to a same surface or a different surface of theelectroactive layer as the first electrode, the electroactive layerconfigured to vibrate responsive to applying a voltage differencebetween the second electrode and the first electrode; and a plurality ofbeads dispersed in the electroactive layer, and wherein at least onesurface of the electroactive layer that overlaps the plurality of beadsis convex. Therefore, the surface area of the electroactive layer isincreased so that the blocking force of the touch sensitive element isimproved. As the blocking force of the touch sensitive element isimproved, the touch sensitive element may overcome a load of the displaypanel disposed above and vibrate the display panel with a large force,and the vibration of the touch sensitive element may be easilytransmitted to the user through the display panel.

Other detailed matters of the exemplary embodiments are included in thedetailed description and the drawings.

According to the present disclosure, it is possible to increase asurface area of the electroactive layer using a plurality of beadshaving a diameter which is larger than a thickness of the electroactivelayer and to improve a blocking force of the touch sensitive element.Therefore, the vibration strength of the touch sensitive element may beimproved.

Further, according to the present disclosure, it is possible to increasean overall Young's modulus of the electroactive layer using a pluralityof beads having a Young's modulus which is larger than that of theelectroactive polymer which configures the electroactive layer and toimprove a blocking force of the touch sensitive element. Therefore, thevibration strength of the touch sensitive element may be improved.

Further, according to the present disclosure, the blocking force of thetouch sensitive element is improved so that the touch sensitive elementmay vibrate with a larger force. Therefore, even though the displaypanel is disposed above the touch sensitive element, the vibration ofthe touch sensitive element may be easily transmitted to the userthrough the display panel.

The effects according to the present disclosure are not limited to thecontents exemplified above, and more various effects are included in thepresent specification.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an exploded perspective view of a touch sensitive elementaccording to an exemplary embodiment of the present disclosure;

FIG. 2 is a cross-sectional view taken along the line II-II′ of FIG. 1according to an exemplary embodiment of the present disclosure;

FIG. 3 is a graph for explaining an improved vibration strength of atouch sensitive element according to an exemplary embodiment of thepresent disclosure;

FIG. 4 is a graph for explaining a vibration strength of a touchsensitive element according to an exemplary embodiment of the presentdisclosure according to a diameter of a bead;

FIG. 5 is a graph for explaining a vibration strength of a touchsensitive element according to an exemplary embodiment of the presentdisclosure according to a Young's modulus of a bead;

FIG. 6 is a graph for explaining a vibration strength of a touchsensitive element according to an exemplary embodiment of the presentdisclosure according to a content of a bead;

FIG. 7 is an exploded perspective view of a touch sensitive elementaccording to another exemplary embodiment of the present disclosure;

FIG. 8 is a cross-sectional view taken along the line VIII-VIII′ of FIG.7 according to an exemplary embodiment of the present disclosure;

FIG. 9 is a cross-sectional view of a touch sensitive element accordingto another exemplary embodiment of the present disclosure;

FIG. 10 is a cross-sectional view of a display device according to anexemplary embodiment of the present disclosure;

FIG. 11 is a cross-sectional view of a display device according toanother exemplary embodiment of the present disclosure; and

FIG. 12 is a graph for explaining an improved vibration strength of adisplay device according to an exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Advantages and characteristics of the present disclosure and a method ofachieving the advantages and characteristics will be clear by referringto exemplary embodiments described below in detail together with theaccompanying drawings. However, the present disclosure is not limited toexemplary embodiment disclosed herein but will be implemented in variousforms. The exemplary embodiments are provided by way of example only sothat a person of ordinary skilled in the art can fully understand thedisclosures of the present disclosure and the scope of the presentdisclosure. Therefore, the present disclosure will be defined only bythe scope of the appended claims.

The shapes, sizes, ratios, angles, numbers, and the like illustrated inthe accompanying drawings for describing the exemplary embodiments ofthe present disclosure are merely examples, and the present disclosureis not limited thereto. Further, in the following description of thepresent disclosure, a detailed explanation of known related technologiesmay be omitted to avoid unnecessarily obscuring the subject matter ofthe present disclosure. The terms such as “including,” “having,” and“comprise of” used herein are generally intended to allow othercomponents to be added unless the terms are used with the term “only”.Any references to singular may include plural unless expressly statedotherwise.

Components are interpreted to include an ordinary error range even ifnot expressly stated.

When the position relation between two parts is described using theterms such as “on”, “above”, “below”, and “next to”, one or more partsmay be positioned between the two parts unless the terms are used withthe term “immediately” or “directly” is not used.

When an element or layer is disposed “on” other element or layer,another layer or another element may be interposed directly on the otherelement or therebetween.

Although the terms “first”, “second”, and the like are used fordescribing various components, these components are not confined bythese terms. These terms are merely used for distinguishing onecomponent from the other components. Therefore, a first component to bementioned below may be a second component in a technical concept of thepresent disclosure.

Like reference numerals generally denote like elements throughout thespecification.

A size and a thickness of each component illustrated in the drawings areillustrated for convenience of description, and the present disclosureis not limited to the size and the thickness of the componentillustrated.

The features of various embodiments of the present disclosure can bepartially or entirely adhered to or combined with each other and can beinterlocked and operated in technically various ways as understood bythose skilled in the art, and the embodiments can be carried outindependently of or in association with each other.

Hereinafter, various exemplary embodiments of the present disclosurewill be described in detail with reference to accompanying drawings.

FIG. 1 is an exploded perspective view of a touch sensitive elementaccording to an exemplary embodiment of the present disclosure. FIG. 2is a cross-sectional view taken along the line II-II′ of FIG. 1according to an exemplary embodiment of the present disclosure.Referring to FIGS. 1 and 2, a touch sensitive element 100 includes anelectroactive layer 120, a first electrode 110, a second electrode 140,and a plurality of beads 130.

The first electrode 110 and the second electrode 140 may be disposed onat least one surface of the electroactive layer 120. For example, asillustrated in FIGS. 1 and 2, the first electrode 110 may be disposed ona lower surface of the electroactive layer 120 and the second electrode140 may be disposed on an upper surface of the electroactive layer 120.The first electrode 110 and the second electrode 140 are electrodeswhich apply voltages to the electroactive layer 120 and are formed of aconductive material. Further, in order to secure light transmittance ofthe touch sensitive element 100, the first electrode 110 and the secondelectrode 140 may be formed of a transparent conductive material. Forexample, the first electrode 110 and the second electrode 140 may beformed of a transparent conductive material such as indium tin oxide(ITO), aluminum doped zinc oxide (AZO), fluorine tin oxide (FTO), orsilver-nano wire (AgNW). Further, the first electrode 110 and the secondelectrode 140 may be configured by a metal mesh. That is, the firstelectrode 110 and the second electrode 140 are configured by a metalmesh in which a metal material is disposed in a mesh form so that thefirst electrode 110 and the second electrode 140 may substantially serveas transparent electrodes. However, the components of the firstelectrode 110 and the second electrode 140 are not limited to theabove-described example, but various transparent conductive materialsmay be used as the components of the first electrode 110 and the secondelectrode 140. Th first electrode 110 and the second electrode 140 maybe formed of the same material or formed of different materials.

The electroactive layer 120 includes an electroactive polymer. That is,the electroactive layer 120 is a plate-shaped film formed of anelectroactive polymer which is a polymer material deformed by anelectrical stimulation. When an electric field is applied between thefirst electrode 110 and the second electrode 140, an alignment directionof dipoles in the electroactive polymer which configures theelectroactive layer 120 is modified and thus the electroactive layer 120vibrates by an electrostatic attractive force or repulsive force. Theelectroactive layer 120 is formed of a PVDF based polymer. For example,the electroactive layer 120 may be formed of a PVDF copolymer such aspoly(vinylidene fluoride-trifluoroethylene)(PVDF-TrFE) or a PVDFterpolymer such as poly(vinylidenefluoride-trifluoroethylene-chlorofluoromethylene)(PVDF-TrFE-CFE) orpoly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene)(PVDF-TrFE-CTFE). ThePVDF copolymer and the PVDF terpolymer are ferroelectric polymers orrelaxed ferroelectric polymer and have an advantage in that largevibration may be generated by a low driving voltage. Further, in thePVDF copolymer and the PVDF terpolymer, TrFE is randomly coupled to thePVDF, so that β-phase may be naturally formed by an electronegativitydifference between hydrogen (H) atom and fluorine (F) atom. Therefore,differently from the PVDF homopolymer, a polling process for forming a βphase is not necessary and a manufacturing process of the touchsensitive element 100 is simplified, and a manufacturing cost isreduced. Further, since the transmittance of a film type electroactivelayer 120 is excellent, the touch sensitive element 100 is attached on afront surface of the display panel to be easily applied to the displaydevice.

A plurality of beads 130 is dispersed in the electroactive layer 120 andeach of the beads 130 has a diameter d which is larger than a thicknesst of the electroactive layer 120. Here, the thickness t of theelectroactive layer 120 means a thickness t of the electroactive layer120 when the electroactive layer 120 in which the beads 130 are notdispersed is formed to have a uniform thickness t. For example, asillustrated in FIGS. 1 and 2, when the beads 130 are not dispersed at anouter boundary of the electroactive layer 120, a distance between alower surface and an upper surface of the electroactive layer 120 at theouter boundary of the electroactive layer 120 means a thickness t of theelectroactive layer 120. In this case, the electroactive layer 120 has aminimum thickness t at the outer boundary of the touch sensitive element100 on which beads 130 are not disposed and a diameter d of the bead 130is larger than a minimum thickness t of the electroactive layer 120.Further, a diameter d of the bead 130 means the largest length amongcross-sectional lengths of the bead 130. Even though in FIGS. 1 and 2, aspherical bead 130 is illustrated, a shape of the bead 130 may not beperfectly spherical, but may be elliptical or polyhedral. The diameter dof the bead 130 means the largest length among cross-sectional lengthsof the bead 130.

The plurality of beads 130 has a diameter d which is larger than thethickness t of the electroactive layer 120. Further, the beads 130 aredispersed in the electroactive layer 120 so that at least one surface ofthe electroactive layer 120 may be convex along the surfaces of theplurality of beads 130. The beads 130 are dispersed in a solutionincluding an electroactive polymer and are applied on the firstelectrode 110 together with the solution including the electroactivepolymer. Specifically, the first electrode 110 is formed on a substrateconfigured by glass and the solution in which the beads 130 and theelectroactive polymer are dispersed are applied on the first electrode110. The solution in which the beads 130 and the electroactive polymerare dispersed may be formed by dispersing an electroactive polymermaterial such as a powder type PVDF-TrFE, PVDF-TrFE-CFE orPVDF-TrFE-CTFE in a solvent such as methyl ethyl ketone (MEK) orcyclopentanone and dispersing the beads 130. The solution in which thebeads 130 and the electroactive polymer are dispersed is applied on asubstrate on which the first electrode 110 is formed to have a thicknesst which is smaller than the diameter d of the beads 130. Thereafter, thesolvent is removed by an annealing process, an electroactive layer 120illustrated in FIG. 2 is formed. In the meantime, the solutioncontaining the electroactive polymer covers surfaces of the beads 130 bya surface tension between the solution containing the electroactivepolymer and the beads 130 and when the solvent is removed by theannealing process, a layer formed of the electroactive polymer coversthe surfaces of the beads 130 with a thin thickness. Accordingly, onesurface of the electroactive layer 120 is formed to be convex along thesurfaces of the beads 130. Thereafter, the second electrode 140 isformed. The second electrode 140 is formed to be convex along onesurface of the convex electroactive layer 120.

The plurality of beads 130 has a higher Young's modulus than theelectroactive polymer which configures the electroactive layer 120. Thatis, the plurality of beads 130 is formed of an organic material or aninorganic material having a higher Young's modulus than the PVDFcopolymer or the PVDF terpolymer. For example, when the beads 130 areformed of an organic material, each of the beads 130 may be formed ofany one selected from divinylbenzene (DVB), polystyrene, a PVDF basedpolymer, and acrylic polymer. Further, when the beads 130 are formed ofan inorganic material, each of the beads 130 may be formed of silicon.

The touch sensitive element 100 according to an exemplary embodiment ofthe present disclosure includes beads 130 which are dispersed in theelectroactive layer 120 and have a diameter d larger than the thicknesst of the electroactive layer 120. Therefore, the surface area of theelectroactive layer 120 may be increased and the blocking force of thetouch sensitive element 100 may be increased. Here, the blocking forcerefers to a maximum force which may be generated by vibrating the touchsensitive element 100 and satisfies the relationship of Equation 1.

$\begin{matrix}{F^{\propto}{N( \frac{S}{L} )}Y\; d_{33}V} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

Here, F is a magnitude of the blocking force, N is a number of laminatedelectroactive layers 120, S is a surface area of the electroactive layer120, L is a thickness of the electroactive layer 120, d₃₃ is apiezoelectric coefficient of the electroactive layer 120, Y is a Young'smodulus of the electroactive layer 120, and V is an intensity of avoltage applied to the electroactive layer 120.

The larger the blocking force of the touch sensitive element 100, thelarger the vibration generated by the touch sensitive element 100. Eventhough a structure having a large mass is disposed on the touchsensitive element 100, the touch sensitive element 100 may overcome aload of an upper structure due to gravity with sufficient force.Therefore, the touch sensitive element 100 may vibrate the upperstructure and the vibration of the touch sensitive element 100 may betransmitted through the upper structure.

As mentioned above, the touch sensitive element 100 according to theexemplary embodiment of the present disclosure includes a plurality ofbeads 130 having a diameter d larger than the thickness t of theelectroactive layer 120. Therefore, at least one surface of theelectroactive layer 120 is formed to be convex along the surface of thebeads 130. Therefore, the surface of the electroactive layer 120 may beformed to be concave and convex and the surface area of theelectroactive layer 120 may be increased. As seen from Equation 1, theblocking force of the touch sensitive element 100 is proportional to thesurface area of the electroactive layer 120. As the blocking force ofthe touch sensitive element 100 is improved, the vibration strength ofthe touch sensitive element 100 is improved and an intensity of thevoltage to be applied to the electroactive layer 120 to form a tactilefeedback with the same vibration strength, that is, the driving voltagemay be reduced.

Further, the touch sensitive element 100 according to the exemplaryembodiment of the present disclosure includes beads 130 having a Young'smodulus larger than the Young's modulus of the electroactive polymerwhich configures the electroactive layer 120. Therefore, the overallYoung's modulus of the electroactive layer 120 may be increased. As seenfrom Equation 1, since the blocking force of the touch sensitive element100 is proportional to the Young's modulus of the electroactive layer120, the increase of the Young's modulus of the electroactive layer 120by the beads 130 increases the blocking force of the touch sensitiveelement 100. Accordingly, the vibration strength of the touch sensitiveelement 100 may be further improved. Improvement of the vibrationstrength of the touch sensitive element 100 by the beads 130 will bedescribed with reference to FIG. 3.

FIG. 3 is a graph for explaining an improved vibration strength of atouch sensitive element according to an exemplary embodiment of thepresent disclosure.

FIG. 3 represents vibration accelerations of a touch sensitive element100 according to a comparative embodiment which does not include aplurality of beads 130 and a touch sensitive element 100 according to anexemplary embodiment of the present disclosure which includes theplurality of beads 130. The touch sensitive element 110 according to thecomparative embodiment and the touch sensitive element 100 according tothe exemplary embodiment have the same configuration except whether thebeads 130 are dispersed in the electroactive layer 120. Specifically,both the touch sensitive element 100 according to the comparativeembodiment and the touch sensitive element 100 according to theexemplary embodiment include a first electrode 110, an electroactivelayer 120, and a second electrode 140. The first electrode 110 and thesecond electrode 140 are formed with a thickness of 300 nm using ITO.The electroactive layer 120 is formed using PVDF-TrFE-CFE to have athickness t of 20 μm. Both the touch sensitive element according to thecomparative embodiment and the touch sensitive element 100 according tothe exemplary embodiment are formed to have a square shape having a sizeof 10 cm×10 cm. The graph of FIG. 3 is measured by applying an ACvoltage with a frequency of 100 Hz to the touch sensitive elementaccording to the comparative embodiment and the touch sensitive element100 according to the exemplary embodiment while varying the intensity ofthe AC voltage.

The beads 130 of the touch sensitive element 100 according to theexemplary embodiment is formed using a PVDF homopolymer to have aspherical shape with a diameter d of 50 μm and the beads 130 areuniformly dispersed in the solution containing PVDF-TrFE-CFE. A totalweight of the beads 130 is 20 wt % with respect to the total weight ofPVDF-TrFE-CFE. The electroactive layer 120 according to the exemplaryembodiment is formed by applying a PVDF-TrFE-CFE solution in which beads130 are dispersed on the substrate, primarily annealing the solution ata temperature of 70° C. for 10 minutes, and then secondarily annealingthe solution at a temperature of 100° C. for 60 minutes.

In contrast, the electroactive layer according to the comparativeembodiment is formed by applying a PVDF-TrFE-CFE solution in which beadsare not dispersed on the substrate, primarily annealing the solution ata temperature of 70° C. for 10 minutes, and then secondarily annealingthe solution at a temperature of 100° C. for 60 minutes.

Referring to FIG. 3, it is confirmed that the touch sensitive element100 according to the exemplary embodiment which includes the beads 130has an excellent vibration acceleration G at the same driving voltage ascompared with the touch sensitive element according to the comparativeembodiment which does not include beads. For example, when a drivingvoltage of 400 V is applied to both ends of the first electrode 110 andthe second electrode 140, the touch sensitive element 100 according tothe comparative embodiment vibrates with a vibration acceleration ofapproximately 0.6 G but the touch sensitive element 100 according to theexemplary embodiment vibrates with a vibration acceleration ofapproximately 1.15 G. That is, it is confirmed that the vibrationacceleration of the touch sensitive element 100 according to theexemplary embodiment which includes the beads 130 is approximately twotimes improved as compared with the touch sensitive element according tothe comparative embodiment which does not include the beads 130.

As mentioned above, since the beads 130 have a diameter d larger thanthe thickness t of the electroactive layer 120, at least one surface ofthe electroactive layer 120 may be formed to be convex along the surfaceof the beads 130 and thus the surface area of the electroactive layer120 may be increased. As the surface area of the electroactive layer 120is increased, the blocking force of the touch sensitive element 100including the electroactive layer 120 is increased and the vibrationacceleration of the electroactive layer 120 is improved.

Further, the beads 130 is formed using the PVDF homopolymer having aYoung's modulus which is larger than the Young's modulus ofPVDF-TrFE-CFE which configures the electroactive layer 120 so that theoverall Young's modulus of the electroactive layer 120 may be increased.Therefore, the blocking force of the touch sensitive element 100 isincreased and the vibration acceleration of the touch sensitive element100 may be further improved.

In the meantime, the touch sensitive element 100 according to theexemplary embodiment of FIG. 3 includes beads 130 which have a diameterd larger than the thickness t of the electroactive layer 120 and aYoung's modulus higher than a Young's modulus of PVDF-TrFE-CFE which isan electroactive polymer configuring the electroactive layer 120. Thevibration acceleration of the touch sensitive element 100 may beimproved only using the beads 130 having a diameter d larger than thethickness t of the electroactive layer 120. That is, even though theYoung's modulus of the beads 130 is equal to or lower than that ofPVDF-TrFE-CFE, the increase of the surface area of the electroactivelayer 120 by the diameter d of the beads 130 may improve the blockingforce of the touch sensitive element 100 so that the vibrationacceleration of the touch sensitive element 100 may be improved.

Similarly, even though the diameter d of the beads 130 is equal to orsmaller than the thickness t of the electroactive layer 120, when theYoung's modulus of the beads 130 is higher than that of PVDF-TrFE-CFEwhich configures the electroactive layer 120, the overall Young'smodulus of the electroactive layer 120 may be improved by the beads 130,so that the vibration acceleration of the touch sensitive element 100may be improved.

As a result, there is no need to satisfy both the condition of thediameter d of the beads 130 with respect to the thickness t of theelectroactive layer 120 and the condition of the Young's modulus of thebeads 130. In other words, even though only one of two conditions issatisfied, the vibration acceleration of the touch sensitive element 100may be improved.

In the meantime, each of the beads 130 may have a diameter d appropriateto increase the surface area of the electroactive layer 120.Specifically, the beads 130 have diameters d which are 1.5 to 2 timeslarger than the thickness t of the electroactive layer 120. When thediameter d of the beads 130 is less than 1.5 times the thickness t ofthe electroactive layer 120, the increase of the surface area of theelectroactive layer 120 by the beads 130 may be very small and theblocking force of the touch sensitive element 100 may not besubstantially increased. Further, when the diameter d of the beads 130exceeds two times the thickness t of the electroactive layer 120, anoccupation rate of the beads 130 which does not have a piezoelectriccharacteristic to the electroactive layer 120 is increased. Accordingly,the occupation rate of the electroactive polymer having a piezoelectriccharacteristic is relatively reduced as compared with the beads 130.Therefore, the piezoelectric characteristic of the electroactive layer120 is reduced and the vibration strength of the touch sensitive element100 may be reduced. Further, when the diameter d of the beads 130exceeds two times the thickness t of the electroactive layer 120,surfaces of the beads 130 may excessively protrude from the surface ofthe electroactive layer 120. Furthermore, the solution containing theelectroactive polymer may not cover the surfaces of the beads 130.Therefore, the surfaces of the beads 130 are exposed to the outside andthe exposed surfaces of the beads 130 may serve as defects which do notgenerate the vibration. Accordingly, the vibration strength of the touchsensitive element 100 may be rather reduced.

Even though the plurality of beads 130 having the same diameter d isillustrated in FIG. 2, in some exemplary embodiments, diameters d of thebeads 130 may be different from each other. For example, the diameters dof the beads 130 may have various values within the range which is 1.5to 2 times larger than the thickness t of the electroactive layer 120.

The change of the vibration strength of the touch sensitive element 100according to the diameter d of the beads 130 will be described withreference to FIG. 4.

FIG. 4 is a graph for explaining a vibration strength of a touchsensitive element according to an exemplary embodiment of the presentdisclosure according to a diameter of a bead. The graph of FIG. 4 ismeasured using a touch sensitive element 100 having the sameconfiguration as the touch sensitive element 100 according to theexemplary embodiment of FIG. 3 except for the diameter d of the beads130. That is, the graph of FIG. 4 is measured using a touch sensitiveelement 100 including the electroactive layer 120 with a thickness of 20μm and beads 130 dispersed in the electroactive layer 120 at a weightratio of 20 wt % with respect to a total weight of the PVDF-TrFE-CFEwhich configures the electroactive layer 120.

Referring to FIG. 4, it is understood that as the diameter d of thebeads 130 is increased, the vibration acceleration of the touchsensitive element 100 according to the exemplary embodiment of thepresent disclosure is increased. For example, when the diameter d of thebeads 130 is 30 μm or larger, the diameter d of the beads 130 is 1.5times larger than the thickness t of the electroactive layer 120 whichis 20 μm. When the diameter d of the beads 130 is 20 μm, the vibrationacceleration of the touch sensitive element 100 is approximately 0.75 Gand when the diameter d of the beads 130 is 30 μm, the vibrationacceleration of the touch sensitive element 100 is improved to beapproximately 1.05 G. That is, when the diameter d of the beads 130 is1.5 times or larger than the thickness t of the electroactive layer 120,the vibration acceleration of the touch sensitive element 100 issignificantly improved. In contrast, when the diameter d of the beads130 exceeds two times the thickness t of the electroactive layer 120,that is, the diameter d of the beads 130 exceeds 40 μm in the graph ofFIG. 4, the vibration acceleration of the touch sensitive element 100 isreduced. As mentioned above, when the diameters d of the beads 130 areincreased, the occupation ratio of the beads 130 which do not havepiezoelectric characteristic to the electroactive layer 130 is increasedand the occupation ratio of the electroactive polymer having apiezoelectric characteristic to the electroactive layer 130 is reduced.Therefore, the vibration acceleration of the touch sensitive element 100may be lowered. That is, when the diameter d of the beads 130 is 1.5 to2 times the thickness t of the electroactive layer 120, the vibrationacceleration of the touch sensitive element 100 may be maximized.

Further, in order to sufficiently improve the blocking force of thetouch sensitive element 100, the beads 130 have a Young's modulus whichis two times or higher than the Young's modulus of the electroactivepolymer which configures the electroactive layer 120. When the Young'smodulus of the beads 130 is smaller than two times the Young's modulusof the electroactive polymer, the improvement of the Young's modulus ofthe electroactive layer 120 by the beads 130 may be very small.Therefore, the blocking force of the touch sensitive element 100 may notbe sufficiently improved. This will be described in more detail withreference to FIG. 5.

FIG. 5 is a graph for explaining a vibration strength of a touchsensitive element according to an exemplary embodiment of the presentdisclosure according to a Young's modulus of a bead. The graph of FIG. 5is measured using a touch sensitive element 100 having the sameconfiguration as the touch sensitive element 100 according to theexemplary embodiment of FIG. 3 except for the Young's modulus d of thebeads 130. That is, the graph of FIG. 5 is measured using a touchsensitive element 100 including an electroactive layer 120 formed ofPVDF-TrFE-CFE which has a thickness of 20 μm and a Young's modulus of 2Gpa.

Referring to FIG. 5, it is understood that when the Young's modulus ofthe beads 130 is approximately two times or higher than the Young'smodulus of the electroactive polymer which configures the electroactivelayer 120, the vibration acceleration of the touch sensitive element 100is improved. For example, it is understood that when the Young's modulusof the beads 130 is 2 Gpa, the vibration acceleration of the touchsensitive element 100 is approximately 0.55 G and when the Young'smodulus of the beads 130 is 8 Gpa, the vibration acceleration of thetouch sensitive element 100 is increased to approximately 1.05 G. Inthis case, as mentioned above, the beads 130 may be formed of an organicmaterial including any one selected from DVB, polystyrene, a PVDF basedpolymer, and acrylic-based polymer or an inorganic material includingsilicon so that the Young's modulus is higher than the Young's modulusof the electroactive polymer.

In the meantime, the beads 130 may be dispersed in the electroactivelayer 120 at an appropriate content to maximize the vibration strengthof the touch sensitive element 100. For example, the beads 130 may bedispersed at 10 wt % to 20 wt % with respect to a total weight of theelectroactive polymer which configures the electroactive layer 120. Whenthe weight ratio of the beads 130 is lower than 10 wt %, the increase ofthe surface area of the electroactive layer 120 by the beads 130 or theincrease in the Young's modulus of the electroactive layer 120 by thebeads 130 may be very small. Further, the increase of the blocking forceof the touch sensitive element 100 by the beads 130 may hardly affectthe improvement of the vibration strength of the touch sensitive element100. Further, when the weight ratio of the beads 130 exceeds 20 wt %,the beads 130 may rather reduce the vibration of the electroactive layer120. As mentioned above, the beads 130 may be formed of an organicmaterial including any one selected from DVB, polystyrene, a PVDF basedpolymer, and acrylic-based polymer or an inorganic material includingsilicon which do not have the piezoelectric characteristic. When theweight ratio of the beads 130 exceeds 20 wt %, the content of theelectroactive polymer may be relatively reduced as compared with thebeads 130. By doing this, the vibration of the electroactive polymer maybe reduced and the vibration acceleration of the touch sensitive element100 may be lowered. Further, when the content of the beads 130 isincreased, the beads 130 are aggregated with each other to be providedas a lump in the electroactive layer 120. In this case, in the regionwhere the beads 130 are aggregated, the vibration is not generated sothat the overall vibration acceleration of the touch sensitive element100 may be reduced. Change in the vibration acceleration of the touchsensitive element 100 according to the content of the beads 130 will bedescribed with reference to FIG. 6.

FIG. 6 is a graph for explaining a vibration strength of a touchsensitive element according to an exemplary embodiment of the presentdisclosure according to a content of a bead. The graph of FIG. 6 ismeasured using a touch sensitive element 100 having the sameconfiguration as the touch sensitive element 100 according to theexemplary embodiment of FIG. 3 except for the contents of the beads 130.Specifically, the graph of FIG. 6 is measured using a touch sensitiveelement 100 including an electroactive layer 120 which is formed ofPVDF-TrFE-CFE and has a thickness of 20 μm and spherical beads 130having a diameter d of 50 μm.

Referring to FIG. 6, it is confirmed that when the weight ratio of thebeads 130 is 10 wt % or higher with respect to the total weight ofPVDF-TrFE-CFE which configures the electroactive layer 120, thevibration acceleration is significantly improved. For example, it isunderstood that when the weight ratio of the beads 130 is 5 wt %, thevibration acceleration of the touch sensitive element 100 isapproximately 0.75 G and when the weight ratio of the beads 130 is 10 wt%, the vibration acceleration of the touch sensitive element 100 isincreased to approximately 1.0 G. In contrast, it is understood thatwhen the weight ratio of the beads 130 exceeds 20 wt %, the vibration ofthe electroactive layer 120 is interrupted by the beads 130 so that thevibration acceleration of the touch sensitive element 100 issignificantly lowered. Accordingly, the weight ratio of the beads 130may be desirably 10 wt % to 20 wt % with respect to the total weight ofthe electroactive polymer of the electroactive layer 120.

FIG. 7 is an exploded perspective view of a touch sensitive elementaccording to another exemplary embodiment of the present disclosure.FIG. 8 is a cross-sectional view taken along the line VIII-VIII′ of FIG.7 according to one exemplary embodiment of the present disclosure. Atouch sensitive element 700 illustrated in FIGS. 7 and 8 is the same asthe touch sensitive element 100 illustrated in FIGS. 1 and 2 except thata first electrode 710 and a second electrode 740 are disposed on thesame surface of the electroactive layer 120. Therefore, a redundantdescription will be omitted.

Referring to FIGS. 7 and 8, the first electrode 710 and the secondelectrode 740 are disposed on the same surface of the electroactivelayer 120. In this case, a horizontal electric field may be generatedbetween the first electrode 710 and the second electrode 740 based on apotential difference between the first electrode 710 and the secondelectrode 740. The electroactive layer 120 may vibrate based on thehorizontal electric field between the first electrode 710 and the secondelectrode 740.

A touch sensitive element 700 according to another exemplary embodimentof the present disclosure includes the first electrode 710 and thesecond electrode 740 formed on the same surface of the electroactivelayer 120. Therefore, the touch sensitive element 700 may provideexcellent visibility. When the touch sensitive element 700 is disposedabove the display panel which displays an image, the visibility of thedisplay panel may be lowered due to the touch sensitive element 700.Specifically, the first electrode 710 and the second electrode 740 maybe formed of a transparent conductive material. Even though the firstelectrode 710 and the second electrode 740 are formed of a transparentconductive material, a part of light which is incident onto the firstelectrode 710 and the second electrode 740 may be reflected or absorbedby the first electrode 710 and the second electrode 740. Therefore,since there is light which does not pass through the first electrode 710and the second electrode 740 among the light which is incident onto thefirst electrode 710 and the second electrode 740, the lighttransmittance of the touch sensitive element 700 may be lowered due tothe first electrode 710 and the second electrode 740. Specifically, whenthe first electrode 710 and the second electrode 740 are disposed onboth surfaces of the electroactive layer 120, the light transmittancemay be further lowered due to the first electrode 710 and the secondelectrode 740. However, in the touch sensitive element 700 according tothe exemplary embodiment of the present disclosure, the first electrode710 and the second electrode 740 formed of a transparent conductivematerial are disposed on one surface of the electroactive layer 120.Therefore, the number of electrodes through which the light incidentonto the touch sensitive element 700 passes is reduced, so that thetransmittance of the touch sensitive element 700 may be improved ascompared with the case when the first electrode 710 and the secondelectrode 740 are disposed on different surfaces of the electroactivelayer 120.

In the meantime, the electroactive layer 120 which is disposed below thefirst electrode 710 and the second electrode 740 includes a convexsurface along the surfaces of the beads 130 dispersed therein.Therefore, the surface area of the electroactive layer 120 is increaseddue to the beads 130 and the blocking force of the touch sensitiveelement 700 is increased.

Further, the beads 130 have a Young's modulus higher than the Young'smodulus of the electroactive polymer which configures the electroactivelayer 120. Therefore, the overall Young's modulus of the electroactivelayer 120 is increased and the blocking force of the touch sensitiveelement 700 may be increased.

As the blocking force of the touch sensitive element 700 is increased,the vibration strength of the touch sensitive element 700 is increased.Therefore, even though a heavy structure is disposed above the touchsensitive element 700, the touch sensitive element 700 may vibrate thestructure by a large force and the vibration of the touch sensitiveelement 700 may be transmitted through the structure.

FIG. 9 is a cross-sectional view of a touch sensitive element accordingto another exemplary embodiment of the present disclosure. A touchsensitive element 900 illustrated in FIG. 9 is the same as the touchsensitive element 100 illustrated in FIGS. 1 and 2 except that anelectroactive layer 920 includes a protrusion 921 protruding between theplurality of beads 130. Therefore, a redundant description will beomitted.

Referring to FIG. 9, the electroactive layer 920 includes a plurality ofprotrusions 921. The protrusions 921 are located between regions wherethe plurality of beads 130 is disposed and have a shape in which a lowersurface and an upper surface of the electroactive layer 920 upwardlyprotrude. Therefore, the upper surface of the electroactive layer 920 isconvex in regions corresponding to the plurality of protrusions 921 andthe plurality of beads 130 and the surface area of the electroactivelayer 920 is increased.

The protrusions 921 of the electroactive layer 920 are formed using asubstrate having protruding patterns corresponding to the protrusions921. Specifically, the first electrode 910 is formed on a substratehaving a plurality of protruding patterns. A first electrode 910 isformed to cover the upper surface of the substrate so that asillustrated in FIG. 9 so that the first electrode 910 is formed to bebent along the protruding patterns of the substrate.

Thereafter, the electroactive layer 920 is formed on the first electrode910. As mentioned above, the electroactive layer 920 is formed bydispersing the electroactive polymer in a solvent, dispersing theplurality of beads 130 in a solution containing the electroactivepolymer, applying the solution in which the beads 130 and theelectroactive polymer are dispersed on the first electrode 910, and thenremoving the solvent by an annealing process. When a thickness of theprotruding pattern of the first electrode 910 is larger than thethickness of the applied solution and the diameters of the beads 130 arelarger than the thickness of the applied solution, the solution maythinly cover the surface of the protruding pattern of the firstelectrode 910 and the surface of the beads 130 by a surface tension ofthe first electrodes 910 and the surface tension of the beads 130.Further, when the solvent is removed by the annealing process, asillustrated in FIG. 9, the electroactive layer 920 having a concave andconvex surface may be formed.

Thereafter, a second electrode 940 is formed on the electroactive layer920. The second electrode 940 is formed to cover the upper surface ofthe electroactive layer 920 so that the second electrode may be formedto be bent along the upper surface of the electroactive layer 920.Thereafter, a substrate having a plurality of protruding patterns isremoved. As the substrate is removed, a touch sensitive element 900 hasthe first electrode 910 which is bent in a region corresponding to theprotrusion 921, the electroactive layer 920 having a protruding uppersurface in the region corresponding to the protrusions 921 and the beads130, and the second electrode 940 which is bent along the surfaces ofthe protrusions 921 and the beads 130 is produced.

A touch sensitive element 900 according to another exemplary embodimentof the present disclosure includes an electroactive layer 920 includinga plurality of protrusions 921 and a plurality of beads 130 having adiameter larger than the thickness of the electroactive layer 920.Therefore, at least one surface of the electroactive layer 920 is convexalong the surfaces of the protrusions 921 and the beads 130 and thesurface area of the electroactive layer 920 is increased due to theprotrusions 921 and the beads 130. Accordingly, the blocking force ofthe touch sensitive element 900 is increased and the touch strength ofthe touch sensitive element 900 is improved.

FIG. 10 is a cross-sectional view of a display device according to anexemplary embodiment of the present disclosure. The touch sensitiveelement 100 included in the display device 1000 of FIG. 10 is the sameas the touch sensitive element 100 according to the exemplary embodimentof the present disclosure which has been described with reference toFIGS. 1 and 2. Therefore, a redundant description of the touch sensitiveelement 100 will be omitted.

Referring to FIG. 10, a display device 1000 includes a display panel1060, a touch sensitive element 100, a touch element 1070, a structure1050, and an adhesive member 1080. In FIG. 10, specific illustration ofthe components of the touch element 1070, the display panel 1060 and thestructure 1050 will be omitted.

The display panel 1060 refers to a panel in which a display element fordisplaying an image in the display device 1000 is disposed. As thedisplay panel 1060, for example, various display panels such as anorganic light emitting display panel, a liquid crystal display panel,and an electro phoretic may be used.

The touch element 1070 refers to a panel which senses a user's touchinput to the display device 1000. As the touch panel 1070, for example,a capacitive type, a resistive type, a surface ultrasonic wave type, oran infrared ray type may be used, but a capacitive type touch elementmay be used as the touch element 1070. In this case, a user may directlyapply a touch input onto a screen of the display panel 1060 by means ofthe touch element 1070 disposed on the display panel 1060, so thatmanipulation of the display device 1000 may be more easily performed.Further, the touch sensitive element 100 may provide a tactile feedbackcorresponding to the user's touch input. Therefore, the user maysimultaneously receive not only visual information but also tactileinformation through the display device 1000.

The structure 1050 is disposed below the touch sensitive element 100 andmay include various components according to the type of display panel1060. For example, when the display panel 1060 is a liquid crystaldisplay panel including liquid crystal, the structure 1050 may include abacklight unit which provides light to the display panel 1060. Further,when the display panel 1060 is an organic light emitting display panelincluding an organic light emitting diode, the structure 1050 mayinclude any one of a heat radiating sheet, a pressure sensor, and a backcover. The heat radiating sheet is a sheet which externally dischargesheat generated from the components disposed on the structure 1050 andmay be formed of a metal having excellent thermal conductivity. Thepressure sensor is a sensor which may measure an intensity of a user'stouch input and may be implemented as a capacitance type. For example,the pressure sensor may be configured of two opposing electrodes and anelastic insulating member disposed between two electrodes. An intervalbetween two electrodes changes in accordance with the user's touch inputso that the capacitance change generated thereby is measured to measurean intensity of a touch pressure. The back cover is a member whichprotects lower portions of the display panel 1060 and the touchsensitive element 100 and is formed of metal or plastic.

The touch sensitive element 100 is disposed below the display panel 1060and includes a first electrode 110, an electroactive layer 120, aplurality of beads 130, and a second electrode 140. The beads 130 have adiameter larger than a thickness of the electroactive layer 120 and onesurface of the electroactive layer 120 has a convex shape along thesurfaces of the beads 130. Therefore, the surface area of theelectroactive layer 120 is increased and the blocking force of the touchsensitive element 100 is increased. As the blocking force of the touchsensitive element 100 is increased, the touch sensitive element 100 mayvibrate the display panel 1060 and the touch element 1070 disposed abovethe touch sensitive element 100 with a large force.

Specifically, the user applies touch input to an upper portion of thetouch element 1070 and the vibration of the touch sensitive element 100needs to be transmitted to the user through the display panel 1060 andthe touch element 1070. As mentioned above, the display panel 1060 andthe touch element 1070 are disposed above the touch sensitive element100 so that a load may be applied to the touch sensitive element 100 dueto weights of the display panel 1060 and the touch element 1070. Whenthe blocking force of the touch sensitive element 100 is small, thevibration of the touch sensitive element 100 does not overcome the loaddue to the weight of the display panel 1060 and the touch element 1070so that the vibration of the touch sensitive element 100 may not betransmitted to the user.

However, the touch sensitive element 100 according to the exemplaryembodiment of the present disclosure includes beads 130 having adiameter larger than the thickness of the electroactive layer 120 andthe surface area of the electroactive layer 120 is increased due to thebeads 130. Therefore, the blocking force of the touch sensitive element100 is increased. Therefore, the touch sensitive element 100 may vibratewith a large force and the vibration of the touch sensitive element 100may sufficiently overcome the load due to the weights of the displaypanel 1060 and the touch element 1070. Accordingly, the touch sensitiveelement 100 vibrates the display panel 1060 and the touch element 1070and the vibration of the touch sensitive element 100 may be transmittedto the user through the display panel 1060 and the touch element 1070.

Further, when the Young's modulus of the plurality of beads 130 ishigher than the Young's modulus of the electroactive polymer whichconfigures the electroactive layer 120, the overall Young's modulus ofthe electroactive layer 120 is increased by the beads 130 and theblocking force of the touch sensitive element 100 may be furtherincreased. Therefore, the vibration of the touch sensitive element 100may be further satisfactorily transmitted to the user through thedisplay panel 1060 and the touch element 1070.

In the meantime, since the touch sensitive element 100 is disposed belowthe display panel 1060, the interruption of the image implemented in thedisplay panel 1060 due to the touch sensitive element 100 may beminimized. That is, the lowering of visibility due to the touchsensitive element 100 may be minimized. As mentioned above, the firstelectrode 110, the second electrode 140, and the electroactive layer 120of the touch sensitive element 100 have small thicknesses andtransparency. Nevertheless, a part of light emitted from the displaypanel 1060 may be reflected or scattered from the surfaces of the firstelectrode 110, the second electrode 140, and the electroactive layer120, so that the visibility of the display panel 1060 may be lowered.However, in the display device 1000 according to the exemplaryembodiment of the present disclosure, the touch sensitive element 100 isdisposed below the display panel 1060 so that the lowering of visibilitydue to the touch sensitive element 100 may be minimized and the imageimplemented in the display panel 1060 may be clearly seen.

In the meantime, the touch sensitive element 100 and the display panel1060 may be adhered to each other by means of the adhesive member 1080.The adhesive member 1080 has a thickness larger than a height of aportion where the second electrode 140 is bent so as to cover the convexsurface of the touch sensitive element 100. For example, the adhesivemember 1080 has a thickness of 10 μm or larger. In this case, the bentportion of the second electrode 140 is covered by the adhesive member1080 and the display panel 1060 and the touch sensitive element 100 maybe firmly adhered to each other by the adhesive member 1080.

FIG. 11 is a cross-sectional view of a display device according toanother exemplary embodiment of the present disclosure. A display device1100 of FIG. 11 is the same as the display device 1000 of FIG. 10 exceptthat a touch element is omitted and a structure 1150 is disposed abovethe touch sensitive element 100 so that a redundant description will beomitted.

Referring to FIG. 11, the display device 1100 according to anotherexemplary embodiment of the present disclosure includes a touch elementintegrated display panel 1160 including a plurality of touch electrodes.The touch element integrated display panel 1160 may be a liquid crystaldisplay panel including a plurality of touch electrodes. The touchelectrode may serve as a pixel electrode or a common electrode of theliquid crystal display panel. In this case, a common voltage or a pixelvoltage is applied to the touch electrode during a display interval whenthe image is displayed on the display panel 1160, and a touch voltage isapplied to the touch electrode during a touch sensing interval when thetouch input is sensed. However, the present disclosure is not limitedthereto and the display panel 1160 may be an organic light emittingdisplay panel 1160 including a plurality of touch electrodes. In thiscase, the touch electrode may be disposed below an upper substrate ofthe organic light emitting display panel 1160 or above an encapsulationlayer which encapsulates the organic light emitting diode.

A structure 1150 may be disposed below the display panel 1160 and mayinclude various components according to the type of display panel 1160.For example, when the display panel 1160 is implemented as a touchelement integrated liquid crystal display panel 1160, the structure 1150may include a backlight unit.

In the display device 1100 according to another exemplary embodiment ofthe present disclosure, since a plurality of touch electrodes isprovided on the display panel 1160, a separate touch element may beomitted. Therefore, an entire thickness of the display device 1100 maybe reduced and a thin and light display device 1100 may be provided.

Further, the display device 1100 according to another exemplaryembodiment of the present disclosure includes a touch sensitive element100 disposed below the structure 1150, so that the lowering of thevisibility due to the touch sensitive element 100 may not be caused.Specifically, when the display panel 1160 is the touch elementintegrated liquid crystal display panel 1160, the structure 1150 belowthe display panel 1160 may include a backlight unit. When the touchsensitive element 100 is disposed between the display panel 1160 and thestructure 1150, light generated in the backlight unit of the structure1150 may be reflected or scattered while passing through the touchsensitive element 100. Further, a part of light which is not reflectedor scattered by the touch sensitive element 100 may be provided to thedisplay panel 1160. In this case, the brightness of the light of thebacklight unit may be reduced by the touch sensitive element 100 and thevisibility of the display panel 1160 may be lowered. However, thedisplay device 1100 according to another exemplary embodiment of thepresent disclosure includes a touch sensitive element 100 disposed belowthe structure 1150, so that all light of the backlight unit may betransmitted to the display panel 1160 and the lowering of the visibilitydue to the touch sensitive element 100 may not be caused.

Specifically, the touch sensitive element 100 includes a plurality ofbeads 130 having a diameter which is larger than the thickness of theelectroactive layer 120 so that the surface area of the electroactivelayer 120 may be increased. Further, when the Young's modulus of theplurality of beads 130 is higher than the Young's modulus of theelectroactive polymer which configures the electroactive layer 120, theentire Young's modulus of the electroactive layer 120 may be increaseddue to the beads 130. The increase of the surface area of theelectroactive layer 120 and the increase of the Young's modulus of theelectroactive layer 120 improve the blocking force of the touchsensitive element 100. As the blocking force of the touch sensitiveelement 100 is improved, the touch sensitive element 100 may vibratewith a large force. Accordingly, even though the display panel 1160 andthe structure 1150 are disposed above the touch sensitive element 100,the vibration of the touch sensitive element 100 may be transmitted tothe user through the display panel 1160 and the structure 1150.

An improved vibration strength of the display device according to theexemplary embodiment of the present disclosure will be described withreference to FIG. 12.

FIG. 12 is a graph for explaining an improved vibration strength of adisplay device according to an exemplary embodiment of the presentdisclosure.

In FIG. 12, both a display device according to a comparative embodimentand a display device according to the exemplary embodiment include thesame configuration except for the touch sensitive element. Specifically,both a display device according to a comparative embodiment and adisplay device according to the exemplary embodiment include a touchelement integrated liquid crystal display panel disposed on the touchsensitive element. A weight of the liquid crystal display panel is 74 g.

In the meantime, both a touch sensitive element of the display deviceaccording to a comparative embodiment and a touch sensitive element ofthe display device according to the exemplary embodiment include a firstelectrode, an electroactive layer, and a second electrode. The firstelectrode and the second electrode are formed to have a thickness of 300nm using ITO. The electroactive layer is formed using PVDF-TrFE-CFE tohave a thickness of 20 μm. Both the touch sensitive element according tothe comparative embodiment and the touch sensitive element according tothe exemplary embodiment are formed to have a square shape having a sizeof 10 cm×10 cm. A graph of FIG. 12 is measured by applying an AC voltageof 400 V and 100 Hz to the touch sensitive element of the display deviceaccording to the comparative embodiment and the touch sensitive elementof the display device according to the exemplary embodiment.

The touch sensitive element of the display device according to theexemplary embodiment includes a plurality of spherical beads having adiameter d of 50 μm using a PVDF homopolymer. The beads are uniformlydispersed in a solution containing PVDF-TrFE-CFE and a total weight ofthe beads is 20 wt % with respect to the total weight of PVDF-TrFE-CFE.

As illustrated in FIG. 12, it is understood that the display deviceaccording to the comparative embodiment includes a touch sensitiveelement which does not include beads, so that the vibration of the touchsensitive element does not sufficiently vibrate the display panel. Thatis, since the touch sensitive element of the display device according tothe comparative embodiment does not include beads, the touch sensitiveelement has a small blocking force and does not sufficiently vibrate thedisplay panel of 74 g. In contrast, the display device according to theexemplary embodiment includes the touch sensitive element includingbeads. The beads have a diameter larger than the thickness of theelectroactive layer and have a Young's modulus larger than the Young'smodulus of the electroactive polymer which configures the electroactivelayer. Therefore, the blocking force of the touch sensitive element isincreased and the touch sensitive element vibrates with a large force,so that the display panel of 74 g disposed on the touch sensitiveelement may sufficiently vibrate. As a result, the display deviceaccording to the exemplary embodiment has a larger vibration strengththan that of the display device according to the comparative embodiment.

The exemplary embodiments of the present disclosure can also bedescribed as follows:

According to an aspect of the present disclosure, the touch sensitiveelement includes an electroactive layer, an electrode, and a pluralityof beads. The electroactive layer includes an electroactive polymer. Theelectrode is disposed on at least one surface of the electroactivelayer. The plurality of beads is dispersed in the electroactive layerand has a diameter larger than a thickness of the electroactive layer.The touch sensitive element according to an exemplary embodiment of thepresent disclosure includes a plurality of beads having a diameterlarger than a thickness of the electroactive layer. Therefore, at leastone surface of the electroactive layer is formed to be convex along thesurfaces of the plurality of beads and the surface area of theelectroactive layer is increased. Accordingly, the blocking force of thetouch sensitive element may be improved and the vibration strength ofthe touch sensitive element may be improved.

The plurality of beads may have a Young's modulus higher than a Young'smodulus of the electroactive polymer.

Diameters of the plurality of beads may be 1.5 to 2 times the thicknessof the electroactive layer.

A total weight of the plurality of beads is 10 wt % to 20 wt % withrespect to a weight of the electroactive polymer.

The electroactive polymer is at least one of poly(vinylidenefluoride-trifluoroethylene)(PVDF-TrFE), poly(vinylidenefluoride-trifluoroethylene-chlorofluoromethylene (PVDF-TrFE-CFE), andpoly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene(PVDF-TrFE-CTFE).

The plurality of beads is formed of an organic material including anyone selected from divinylbenzene (DVB), polystyrene, a PVDF basedpolymer, and an acrylic-based polymer or an inorganic material includingsilicon.

The electroactive layer may include a protrusion protruding in a regionbetween the plurality of beads.

The electrode includes a first electrode and a second electrode. Thefirst electrode may be located on a lower surface of the electroactivelayer and may be bent along the lower surface of the electroactive layerin a region corresponding to the protrusion. The second electrode may belocated on an upper surface of the electroactive layer and may be bentalong the upper surface of the electroactive layer in a regioncorresponding to the protrusion and a region corresponding to the beads.

According to another aspect of the present disclosure, a touch sensitiveelement includes an electroactive layer, an electrode, and a pluralityof beads. The electroactive layer includes an electroactive polymer. Theelectrode may be disposed on at least one surface of the electroactivelayer. The plurality of beads may be dispersed in the electroactivelayer and have a Young's modulus higher than a Young's modulus of theelectroactive polymer. The touch sensitive element according to anotherexemplary embodiment of the present disclosure includes the plurality ofbeads having a Young's modulus higher than that of the electroactivepolymer, so that the entire Young's modulus of the electroactive layermay be improved. Accordingly, the blocking force of the touch sensitiveelement may be improved and the vibration strength of the touchsensitive element may be improved.

Diameters of the plurality of beads are larger than the thickness of theelectroactive layer.

The plurality of beads has a Young's modulus which is two times higherthan a Young's modulus of the electroactive polymer.

According to an aspect of the present disclosure, a display deviceincludes a display panel and a touch sensitive element. The displaypanel displays an image. The touch sensitive element is disposed belowthe display panel and includes an electroactive layer, an electrode, anda plurality of beads. The electrode of the touch sensitive element isdisposed on at least one surface of the electroactive layer. Theplurality of beads is dispersed in the electroactive layer. At least onesurface of the electroactive layer is convex along the plurality ofbeads. The display device according to an exemplary embodiment of thepresent disclosure includes a touch sensitive element including anelectroactive layer in which at least one surface is convex along theplurality of beads. Therefore, the surface area of the electroactivelayer is increased so that the blocking force of the touch sensitiveelement is improved. As the blocking force of the touch sensitiveelement is improved, it is possible to overcome the load of the displaypanel disposed above and vibrate the display panel with high vibrationand the vibration of the touch sensitive element may be easilytransmitted to the user through the display panel.

Diameters of the plurality of beads are larger than a minimum thicknessof the electroactive layer.

The display device may further include a backlight unit disposed belowthe display panel, the display panel may be a liquid crystal displaypanel and the touch sensitive element may be disposed below thebacklight unit.

The display panel may be an organic light emitting display panel.

The display device may further include a touch element on the displaypanel.

Although the exemplary embodiments of the present disclosure have beendescribed in detail with reference to the accompanying drawings, thepresent disclosure is not limited thereto and may be embodied in manydifferent forms without departing from the technical concept of thepresent disclosure. Therefore, the exemplary embodiments of the presentdisclosure are provided for illustrative purposes only but not intendedto limit the technical spirit of the present disclosure. The scope ofthe technical spirit of the present disclosure is not limited thereto.Therefore, it should be understood that the above-described exemplaryembodiments are illustrative in all aspects and do not limit the presentdisclosure. The protective scope of the present disclosure should beconstrued based on the following claims, and all the technical conceptsin the equivalent scope thereof should be construed as falling withinthe scope of the present disclosure.

What is claimed is:
 1. A touch sensitive element, comprising: anelectroactive layer including an electroactive polymer; a firstelectrode electrically coupled to a surface of the electroactive layer;a second electrode electrically coupled to a same surface or a differentsurface of the electroactive layer as the first electrode, theelectroactive layer configured to vibrate responsive to applying avoltage difference between the second electrode and the first electrode;and a plurality of beads dispersed in the electroactive layer, theplurality of beads having a diameter that is larger than a thickness ofthe electroactive layer without applying the voltage difference betweenthe second electrode and the first electrode.
 2. The touch sensitiveelement according to claim 1, wherein the plurality of beads has aYoung's modulus that is greater than a Young's modulus of theelectroactive polymer.
 3. The touch sensitive element according to claim1, wherein diameters of the plurality of beads are 1.5 to 2 times thethickness of the electroactive layer.
 4. The touch sensitive elementaccording to claim 1, wherein a total weight of the plurality of beadsis 10% to 20% of a weight of the electroactive polymer.
 5. The touchsensitive element according to claim 1, wherein the electroactivepolymer is at least one of poly(vinylidenefluoride-trifluoroethylene)(PVDF-TrFE), poly(vinylidenefluoride-trifluoroethylene-chlorofluoromethylene (PVDF-TrFE-CFE), orpoly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene(PVDF-TrFE-CTFE).
 6. The touch sensitive element according to claim 5,wherein the plurality of beads comprises an organic material includingone selected from divinylbenzene (DVB), polystyrene, a PVDF basedpolymer, an acrylic based polymer, or an inorganic material includingsilicon.
 7. The touch sensitive element according to claim 1, whereinthe electroactive layer includes a protrusion protruding from a firstsurface of the electroactive layer towards a second surface of theelectroactive layer that is above the first surface, the protrusionbetween at least a pair of beads from the plurality of beads.
 8. Thetouch sensitive element according to claim 7, wherein the firstelectrode which is on the first surface of the electroactive layer andthe first electrode is bent along the first surface of the electroactivelayer that comprises to the protrusion; and wherein the second electrodeis located on the second surface of the electroactive layer and is bentalong the second surface of the electroactive layer that overlaps theprotrusion and at least one of the plurality of beads.
 9. A touchsensitive element, comprising: an electroactive layer including anelectroactive polymer; a first electrode electrically coupled to asurface of the electroactive layer; a second electrode electricallycoupled to a same surface or a different surface of the electroactivelayer as the first electrode, the electroactive layer configured tovibrate responsive to applying a voltage difference between the secondelectrode and the first electrode; and a plurality of beads dispersed inthe electroactive layer, the plurality of beads having a Young's modulusthat is greater than a Young's modulus of the electroactive polymer,wherein a total weight of the plurality of beads is 10% to 20% of aweight of the electroactive polymer.
 10. The touch sensitive elementaccording to claim 9, wherein diameters of the plurality of beads arelarger than a thickness of the electroactive layer.
 11. The touchsensitive element according to claim 9, wherein the plurality of beadshas a Young's modulus which is two times higher than a Young's modulusof the electroactive polymer.
 12. A display device, comprising: adisplay panel which displays an image; and a touch sensitive elementbelow the display panel, the touch sensitive element including: anelectroactive layer; a first electrode electrically coupled to a surfaceof the electroactive layer; a second electrode electrically coupled to asame surface or a different surface of the electroactive layer as thefirst electrode, the electroactive layer configured to vibrateresponsive to applying a voltage difference between the second electrodeand the first electrode; and a plurality of beads dispersed in theelectroactive layer, and wherein at least one surface of theelectroactive layer that overlaps the plurality of beads is convexwithout applying the voltage difference between the second electrode andthe first electrode.
 13. The display device according to claim 12,wherein diameters of the plurality of beads are larger than a minimumthickness of the electroactive layer.
 14. The display device accordingto claim 12, further comprising: a backlight unit below the displaypanel, wherein the display panel is a liquid crystal display panel, andthe touch sensitive element is disposed below the backlight unit. 15.The display device according to claim 12, wherein the display panel isan organic light emitting display panel.
 16. The display deviceaccording to claim 12, further comprising: a touch element on thedisplay panel.